Working vehicle, control device for working vehicle, and control method for working vehicle

Abstract

A working vehicle in which an output from an engine is distributed to a traveling system and a hydraulic device system includes a loading operation detection unit that detects whether a loading operation using a work equipment is being performed, a clutch contained in the traveling system and connected to a distributor, a maximum output characteristic control unit that selects a second engine maximum output characteristic from among first and second maximum output characteristics when it is detected that the loading operation is being performed, and a hydraulic oil amount control unit that decreases a clutch pressure of the clutch when it is detected that the loading operation is being performed. In the first engine maximum output characteristic, a maximum output torque in a predetermined engine revolution speed range is lower than that in the second engine maximum output characteristic.

The invention claimed is: 
     
       1. A working vehicle comprising:
 an engine; 
 a work equipment; 
 a traveling system; 
 a hydraulic device system provided with a cylinder that actuates the work equipment; 
 a distributor that distributes an output from the engine to the traveling system and the hydraulic device system; 
 a loading operation detection unit that detects whether a loading operation using the work equipment is being performed; 
 a clutch contained in the traveling system and connected to the distributor; 
 a maximum output characteristic control unit that, when it is detected that the loading operation is being performed, selects a second engine maximum output characteristic from among the second maximum output characteristic and a first engine maximum output characteristic in which a maximum output torque in a predetermined engine revolution speed range is lower than that in the second engine maximum output characteristic; and 
 a hydraulic oil amount control unit that decreases a clutch pressure of the clutch when it is detected that the loading operation is being performed. 
 
     
     
       2. The working vehicle according to  claim 1 , wherein
 the hydraulic oil amount control unit performs the following operation (A) and/or (B) in addition to decreasing the clutch pressure of the clutch when it is detected that the loading operation is being performed: 
 (A) increasing a flow rate of hydraulic oil supplied from a first pump from among one or more pumps including the first pump for supplying hydraulic oil to the cylinder; and 
 (B) supplying the hydraulic oil to the cylinder also from a second pump included in the one or more pumps, in addition to the hydraulic oil supplied from the first pump. 
 
     
     
       3. The working vehicle according to  claim 1 , wherein
 the loading operation detection unit determines that the loading operation is being performed when a boom lever is operated to raise the boom and an angle of the boom is equal to or greater than a predetermined angle. 
 
     
     
       4. The working vehicle according to  claim 1 , wherein
 there are at least two groups of conditions from among first to third groups of conditions, and each group of conditions includes at least one condition for determining that the loading operation is being performed, 
 the first group of conditions is a group of conditions relating to expression of operator's will, 
 the second group of conditions is a group of conditions relating to a position of the work equipment, 
 the third group of conditions is a group of conditions relating to a state of the traveling system, and 
 the loading operation detection unit detects that the loading operation is being performed when each of the conditions selected one by one from at least two groups of conditions from among the first to third groups of conditions is satisfied. 
 
     
     
       5. The working vehicle according to  claim 4 , wherein
 the work equipment is a boom provided rotatably at one side of a vehicle body, 
 the cylinder is a boom cylinder for rotating the boom, and 
 the first group of conditions includes at least one of the following conditions (a) and (b): 
 (a) a boom lever is operated to raise the boom; and 
 (b) an extension speed of the boom cylinder takes a positive value. 
 
     
     
       6. The working vehicle according to  claim 4 , wherein
 the work equipment is a boom provided rotatably at one side of a vehicle body, and 
 the second group of conditions includes at least one of the following conditions (c) and (d): 
 (c) an angle of the boom is equal to or greater than a predetermined angle; and 
 (d) an angle of the boom is less than a predetermined maximum angle. 
 
     
     
       7. The working vehicle according to  claim 4 , wherein
 the third group of conditions includes at least one of the following conditions (e) to (h): 
 (e) a ratio of an input revolution speed and an output revolution speed of the clutch when a brake is off is equal to or greater than a predetermined value, or the brake is on; 
 (f) a gear ratio set to the transmission is a predetermined gear ratio; 
 (g) a traveling range set to the transmission has been switched from reverse to forward; and 
 (h) a vehicle speed is equal to or higher than a predetermined speed. 
 
     
     
       8. The working vehicle according to  claim 5 , wherein
 the third group of conditions includes at least one of the following conditions (e) to (h): 
 (e) a ratio of an input revolution speed and an output revolution speed of the clutch when a brake is off is equal to or greater than a predetermined value, or the brake is on; 
 (f) a gear ratio set to the transmission is a predetermined gear ratio; 
 (g) a traveling range set to the transmission has been switched from reverse to forward; and 
 (h) a vehicle speed is equal to or higher than a predetermined speed. 
 
     
     
       9. The working vehicle according to  claim 6 , wherein
 the third group of conditions includes at least one of the following conditions (e) to (h): 
 (e) a ratio of an input revolution speed and an output revolution speed of the clutch when a brake is off is equal to or greater than a predetermined value, or the brake is on; 
 (f) a gear ratio set to the transmission is a predetermined gear ratio; 
 (g) a traveling range set to the transmission has been switched from reverse to forward; and 
 (h) a vehicle speed is equal to or higher than a predetermined speed. 
 
     
     
       10. The working vehicle according to  claim 2 , wherein
 the loading operation detection unit determines that the loading operation is being performed when a boom lever is operated to raise the boom and an angle of the boom is equal to or greater than a predetermined angle. 
 
     
     
       11. The working vehicle according to  claim 2 , wherein
 there are at least two groups of conditions among first to third groups of conditions, and each group of conditions includes at least one condition for determining that the loading operation is being performed,
 the first group of conditions is a group of conditions relating to expression of operator's will, 
 the second group of conditions is a group of conditions relating to a position of the work equipment, 
 the third group of conditions is a group of conditions relating to a state of the traveling system, and 
 the loading operation detection unit detects that the loading operation is being performed when each of the conditions selected one by one from at least two groups of condition from among the first to third groups of conditions is satisfied. 
 
 
     
     
       12. The working vehicle according to  claim 3 , wherein
 there are at least two groups of conditions among first to third groups of conditions, and each group of conditions includes at least one condition for determining that the loading operation is being performed,
 the first group of conditions is a group of conditions relating to expression of operator's will, 
 the second group of conditions is a group of conditions relating to a position of the work equipment, 
 the third group of conditions is a group of conditions relating to a state of the traveling system, and 
 the loading operation detection unit detects that the loading operation is being performed when each of the conditions selected one by one from at least two groups of condition from among the first to third groups of conditions is satisfied. 
 
 
     
     
       13. The working vehicle according to  claim 5 , wherein
 the work equipment is a boom provided rotatably at one side of a vehicle body, and 
 the second group of conditions includes at least one of the following conditions (c) and (d): 
 (c) an angle of the boom is equal to or greater than a predetermined angle; and 
 (d) an angle of the boom is less than a predetermined maximum angle. 
 
     
     
       14. A control device for a working vehicle including an engine, a work equipment, and a traveling system having a clutch, the control device comprising:
 a loading operation detection unit that detects whether a loading operation using the work equipment is being performed; 
 a maximum output characteristic control unit that, when it is detected that the loading operation is being performed, selects a second engine maximum output characteristic from among the second maximum output characteristic and a first engine maximum output characteristic in which a maximum output torque in a predetermined engine revolution speed range is lower than that in the second engine maximum output characteristic; and 
 a hydraulic oil amount control unit that decreases a clutch pressure of the clutch when it is detected that the loading operation is being performed. 
 
     
     
       15. A control method for a working vehicle including an engine, a work equipment, and a traveling system having a clutch, the control method comprising:
 a step of detecting whether a loading operation using the work equipment is being performed; 
 a step of selecting, when it is detected that the loading operation is being performed, a second engine maximum output characteristic from among the second maximum output characteristic and a first engine maximum output characteristic in which a maximum output torque in a predetermined engine revolution speed range is lower than that in the second engine maximum output characteristic; and 
 a step of decreasing a clutch pressure of the clutch when it is detected that the loading operation is being performed.